This invention relates to polyurea polymers and polyurea polymer formulations.
It is known in the art to prepare isocyanate based polymers useful for small molding applications such as molded shoe soles. It is also known in the art to prepare such polymers, particularly polyurea polymers, useful for preparing larger moldings such as automobile fascia and body panels. For example, U.S. Pat. No. 4,218,543 to Weber, et al. discloses preparing elastomeric moldings by a reaction injection molding (RIM) process.
However, using polyurea polymers is not always trouble free. Particularly when the polyurea polymers are filled polymers and are first exposed to humid environments and then exposed to high temperatures, surface defects can be observed. In one common polyurea application, reaction injection molding of automobile body parts, the polyurea part can be exposed to temperatures exceeding 350.degree. F. (177.degree. C.). Polyurea parts containing too much water, when exposed to such high temperatures, can exhibit surface phenomena commonly known in the art as blistering.
Blistering occurs when moisture absorbed into a polyurea part interacts with the polymer to produce gas which accumulates in the part forming a gas pocket. This defect, if severe, can cause an entire part to be rejected resulting in lost raw materials, lost production, increased waste and scrap and, as a result, economic loss to the part producer or to the end-user of the part, or both.
The obvious solutions to the blistering problem, avoiding exposing the polyurea polymer parts to high temperatures, or avoiding exposing the polyurea polymer parts to humid air are not always desirable. Heat curing can impart desirable properties to polyurea parts. Applying heat can also aid in the curing of paint finishes, thereby reducing production time and allowing for increased production rates. Also, as in an automobile production application, a polyurea part may be required to be attached to another article and that article may require a high heat exposure. Controlling the humidity in every phase of polyurea part production could be expensive. Therefore, it would be desirable to prepare polyurea polymers which are stable, that is, do not blister upon exposure to humid air and then elevated temperatures.